Coated material and method of making same



MaYM4,"'1937. J. A. MTTCHELL 2,079,379

COATEDMATERIAL AND METHOD MAKING SAME Filed May 3, 1934 2 Sheets-Sheet l PLAsTlclzEE CoNcENTRATmN PEEMEABILITY 20o PYROXYLIN 4!'0 Asl/mc PAEAFFIN PYEoxYLn/DAHAE RATIOAT Vig. 1.

VALUE -INDICATES Pook SUP AND STORAGE.

l DluTYl. PHTHALATE.

PERM EA ILITY ILTmczEsYL PHosPHATE.

111. DlcYcLoHExYL PHTHAT ATE Ore CYcLoHExYL Aun PHTHALATE.

PEE cE NT PLAsTmzEE PLAsTlclzEE CoNcENTEATToN- PEEMEABTUTY |z51 NITROGEN PYEoxYLTN ECI. El '8 PYRoxYLlN/DANAR RAT\o4/ q: (60 |40 `IND1CATE5 Poole E zo 5MP AND STORAGE. wo LDTEUTYL PHTHALATE. E 8 H TETCEESYL PHosPHATE, D.

IH. DncYcLoHExYL PHTHAL- ATE 02 CYCLOHEAYL ACID PHTHALATE,

Z0 ZZ Z4 26 5 30 32 34 36 PEE CENT PLASTTCIZER NVEITOR.

EY Eff" ATTORNEY. I

J. A. MITCHELL COATED MATERIAL AND METHOD OF MAKING SAME Filed May 3, 1954 2 Sheets-Sheet 2 G m L A F- 5 T A :L H

oAsl/:mc PARAFFm FL .F ETL Mmmm USMWE H M .m0 M TET L AHHLvrw A.. .Hw Pvl D DY. L5M.. NEYED o Im ITTR a .C UKab 7.. A525 ILHN PHTHALATE-ZSL Dlx'ml PHTHALATE.

BLDICYcLoHExYL PHTHAL mmmmmwsw ATE..

56 40 PEE CENT PLASTICIZER 240 SLIP A STORAGE "m, DAMAR 00.00 @mmmae PHTHALATE.

IY. DlcYcLoHExYL PHT HAL-I ATE.

l 52 56 Pme CENT PLASTICIZER .Y M X ATTO l2 N EY.

Patented .May d, 'i937 Zwem@ I 2,079,379 comma Margaret. aan manon or "ri fz.: Sgm

Delaware Application May 3, 1934, Serial No. 723,787

8 Claims.

This invention relates to moistureproong compositions and to means for producing them. It relates more particularly to moistureproof sheet materials having improved surface characteristics both as regards their ability to maintain their individuality under normal conditions of storage and their ability to be mutually sealable upon the application of heat.

With the modern trends of development in the 1o packaging of commodities, especially perishable foodstuis, the need has arisen for a wrapping material which can at once provide physical protection against contamination, preservative action by retaining Within the package the original conditions such as moisture content, and sales appeal by permitting examination of the `package contents Without destroying the wrapper. These needs have been largely fulfilled by the recent introduction to the trade of a wrapping material comprising a transparent base sheet,

such asregenerated cellulose, coated with a'transparent moistureproong composition, which latter may comprise a cellulose derivative, a wax, a resin orfblending agent and a plasticizer.

Prior art wrapping materials were generally of the character of waxed papers and could be at least supercially joined by means of heat and pressure. The wrapping industry is generally provided with expensive equipment designed for heat sealing and will look with favor on -new materials only if they can be adapted to this equipment. Moistureproof wrapping materials such as the coated regenerated cellulose described above also have the property of beingheat sealable to a degree, but the joint is not suiiiciently rugged to satisfy the current demands.

These moistureproof wrapping materials are furnished to the consumer in the form of continuous roll stock or as cut-to-sze sheets. In order that the roll stock will unroll smoothly or the cut-to-Sire sheets separate easily, the surface of the material must be smooth and non-tackyY and there must be no tendency towards caking or.

sticking together during the time of storage which intervenes between manufacture and consumption. The moistureprooiing composition, on the other hand, must be flexible, transparent and sumciently thermoplastic to permit intermingling of -superposed coatings during the brief period of the heat sealing operation with immediate I set-up thereafter although it cannot be so thermoplastic that it willbe aiected by the temperature variations normally encountered in handling or storage. One object of this invention comprises the production of improved mcistureproof lm. A, furlther object of the invention relates to improvements in the manufacture of heat-scalable moistureproof wrapping tissues. A further object of the invention relates to the production of mois- 5 tureproof wrapping tissues which fulfill the requirements for iiexibility and transparency and additionally possess a high degree of surface smoothness, slip and resistance to sticking under' storage conditions. Further objects of the in- 10 vention will appear hereinafter.

This invention is primarily concerned with moistureproong compositions comprising a cellulose nitrate, a moistureproong agent, a plasticizer and a resin or other blending agent. The 15 term moistureproong agent denes the material which serves as the basis for moistureproofness. In the formulation of cellulose nitrate coating compositions it is well mown in the art to use a plasticizing agent to impart exibility 20 to the coating. This is also true in the formulation of cellulose nitrate coating compositions which contain moistureproong agents, but it has been observed that the plasticizer also contributes to the moistureproong property and for 25 the production of highly moistureproof coating compositions more plasticizer is employed than is necessary merely for its plasticizing action. The use of excess plasticizer to accomplish this purpose, however, tends to impair the surface 30 characteristics of the moistureproong coating composition since with increased plasticizer con-- tent the composition becomes softer, stickier and morethermoplastic. The softness and sticmness are objectionable from the point of view of good 35 surface slip and storage. The increased ther- A moplasticity would be advantageous for the improvement of heat sealing properties were it not for the fact that the minimum amount of plasticizer which will adord good heat sealing is so 40 close to the amount which will still avoid softness and tackness that the practical control of such a composition to insure a coated product of uniformly good heat sealing properties and uniformly good surface characteristics is ex- 45 tremely difficult, especially for the commercial production of a continuous coated sheet material. Indeed, many common plasticizers pass' the point which is critical for good surface before the point of satisfactory heat seal is reached. 50 For the purposes of lthis invention, moistureproof materials are defined as those which, in the form of a. thin, continuous and unbroken sheet or film, will permit the passage of not more than 690 grams of water'vapor per 100 square meters per 55 hour over a period of 24 hours at approximately 39.5 C. plus or minus 0.5 C., the relative'humidity of the atmosphere at one side of the film being maintained at least at 98% and the relative humidity of the atmosphere at the other side being maintained at such value as to give a humidity diierential of at least Moistureproong coating compositions are dened as those which, when laid down in the form of thin, continuous, unbroken films, applied uniformly as a coating with a total coating thickness not exceeding 0.0005" to both sides of a sheet of regenerated cellulose of thickness approximately 0.0009", will produce a coated product which is moistureproof.

For the purposes of experimental tests, especially for those materials adaptable as coating compositions, moisture proof materials include those substances, compounds or compositions which, when laid down in the form of a continuous, unbroken lm applied uniformly as a coating with a total coating thickness not exceeding 0.0005" to both sides of a sheet of regenerated cellulose of thickness approximately 0.0009" will produce a coated sheet which will permit the passage therethrough of not more than 690 grams of water vapor per 100 square meters'per hour over a period of approximately 24 hours, at a temperature of 39.5 C. plus or minus 0.5 C. (preferably 39.5 C. plus or minus 2.5 C.) with a water Vapor differential of SM5 mm. (preferably 53.4 plus or minus 0.7 mm.) of mercury. For convenience the number of grams of water vapor passed under these conditions may be referred to as "permeability value. An uncoated sheet of regenerated cellulose having a thickness of approximately 0.0009" will show a permeability value of the order of 6900.

In the foregoing, it is apparent that under the conditions set forth, a moistureproofed regenerated cellulose sheet is capabley of resisting the passage of moisture or water vapor therethrough at least ten times as eectively as the uncoated regenerated cellulose sheet.

The composition may be coated on to the base to give a wide range of coating thicknesses, and where heat sealing is desired, increase in the coating thickness will increase the; heat sealing property of any given composition. For the purpose of this invention, and particularly where the ultimate coated sheet material is to be used as a wrapping tissue, the coating thickness is 0.00002" to 0.0005" and preferably 0.00005" on each side of the base.

When heat sealing properties are desired, it will be found that sheet materials provided with compositions described in this specification -are truly heat sealable in the sense that a heat sealed joint -will be stronger than a joint sealed by means of acetone. Additionally, the joint will be at least as strong as a solvent sealed joint obtained by means of methoxy ethanol. These same considerations apply to films obtained by casting the coating compositions per se.

As indicative of the strength of the heat sealed jointobtainable, the following test has been de vised:

Strips of the coated material 1.5" wide are superposed on one end so that opposite faces of the lm are in contact. A seal is made across the width of the material by imposing thereon a heatediron weighing 1500 grams for 2 seconds. The iron is so designed as to^ cause a seal to be made of a width of 2/32", the iron being maintained in any suitablemanner at a temperature above C. and below 200, C. as, for instance, C. The two strips so sealed are opened at the free ends and placed in a stretching device, such as a Suter testing machine, by gripping each end of the sheet in suitable clamps, one of which is xed while the other is moved away at a constant speed of 12" per minute. The force in grams required to pull the sheets apart is taken as a measure of the bond strength and may be referred to as heat sealing value.

In accordance with this invention, it has now been found that there are certain plasticizers for cellulose nitrate-moistureproong agent coating compositions which are unique iny their ability to plasticize, increase moistureproofness, provide excellent surface and storage characteristics and also impart a high degree of thermo-plasticity which can in turn produce an exceptionally strong heat sealed joint. Dicyclohexyl phthalate and cyclohexyl acid phthalate are the plasticizers which possess this unique property. They may be used alone or in combination with other common plasticizers to produce moistureproong coatings which exhibit a high degree of moistureproofness; good appearance, flexibility and transparency; excellent surface slip and storage without sticking or marring; and excellent heat sealing properties. Among the plasticizers which may be advantageously combined With dicyclohexyl phthalate or cyclohexyl acid phthalate are alkyl phthalates such as dibutyl phthalate, tricresyl, phosphate, dicyclohexyl adipate, esters ofv o-benzoyl benzoic acid, cyclohexyl butyl phthalate, derivatives of toluene sulfonamide and the like. Throughout the balance of this specification reference will be made to dicyolohexyl phthalate,

but it is to be understood that cyclohexyl acid phthalate maybe advantageously .employed although because of its somewhat superior properties, the former is to be preferred.

I have found that cellulose nitrate coating compositions plasticized with dicyclohexyl phthalate exhibit unique properties which may account for the improved surface and storage characteristics. Thus, for example, a composition of nitrocellulose, resin an-d dioyclohexyl phthalate exhibits no plasticity at ordinary temperatures; at least, a film cast from such a composition undergoes no deformation under tensile stress and has a high breaking strength. On the other hand, the composition. is thermoplastic and be- .comes heat-sealable at elevated temperatures.

It is apparent, then, that when a sheet of base material such as regenerated cellulose is coated with a composition of this type the coating retains its normal characteristics. Consequently, the coated sheets will possess good surface slip,

Aand will not be subject to caking, sticking or marring in storage because the coating suffers no deformation under the stresses encountered in storage. The thermoplasticity of the coating at elevated temperatures,- however, affords excellent heat-sealing properties. The same considerations are applicable to compositions comprising a moisture-proofing agent.

ing to the type of coating composition desired. Obviously, for those uses where a transparent coated material is desired, any pigments or modifying agents which will impair the transparency 5 of the coating composition will be omitted therefrom. The proportions of the several ingredients may vary within rather wide limits, depending on the properties desired in the n- .ished composition and these will be more speciiically set forth below and will be illustrated in the several examples.

The invention contemplates only those coating compositions which comprise a cellulose nltrate. Cellulose nitrates of varying degrees of 'l5 conversion such as of various nitrogen contents may be used and, indeed mixtures of different types' of cellulose nitrate may also be used as, for example, mixtures of cellulose nitrates of diierent nitrogen contents. Cellulose nitrate of low nitrogen` content such as 11.5% nitrogen, is generally preferable especially where high heat sealability is desired.

As additional plasticizersior use in combination with those of, this invention, it is possible to use any of the plasticizers mentioned previously as well as such compounds as dilauryl phthalate, di-(methylcyclohexyl) phthalate, di- (dimethylcyclohexyl) phthalate, methyl-(dimethylcyclohexyl) adipate, or the likes As moistureproofing agents, vit is possible to use waxes or wax-like materials such as parafcompatibility of these two ingredients. This ma.- terial is referred to as a blending agent and is usually of a resinous nature although this is not absolutely necessary. When the blending agent is resinous, advantage may be taken of its lm- 5 forming characteristics, if any, and sufcient quantity may be added to 'a coating composition to contribute towards the body and build of that composition in addition to the blending action. Depending on the nature of the blending agent, l0 more or less plasticizing action on the cellulose nitrate may be\ obtained.

As blending agents, any of the natural or synthetic resins commonly available may be used so long as they are compatible and form l5 rvhomogeneous mixtures. Such resins may include ester gum, rosinates, hydrogenated rosin, hydrogenated rosin esters, damar, copal, kauri, glyptals, vinyl derivatives, chlorinated diphenyl resins, soluble resins of the phenol-formalde- 20 hyde type. Non-resinous blending agents may be used when they yield homogeneous mixtures and these may include hydrogenated castor oil, castor oil phthalate, lanolin or wool grease, ethyl abietate, methyl abietate, diethylene glycol rosi- 25 nate, diethylene glycol hydrorosinate or the'like.

As illustrative of moistureproong coating compositions which embody the principles of this invention, the following specific examples are given but they should not be considered in any 30 way as limitative of the scope of this invention.

Table I Examples 35 Solids composition by weight VII VIII IX X XI Cellulose derivative Nitrocellulose (12.5% N) Plaslicizer Dicyclohexyl phthalate Cyclohexyl acid nhfhnlnm N itrocellulose (11.5% N). 48. 0

Dibutyl phthalate Dilamyl pmi-infn l l Blending agent Dewaxed damar Ester gum. Methyl abietate Ethyl-abietate,.-

Diethylene glycol rc im Diethylene glycol hydmm imm.

Wax Asiatic parailin beeswax, certain chlorinated hydrocarbona'Chinese insect wax or other synthetic waxes or waxlike material. If some of these waxes are too i* Soft for the purposes desired, they may be mixed with harder waxes of the group or with carnauba wax, candelilla wax or other harder waxes. Generally, paraffin serves as a satisfactory moistureproofing' agent which may be hardened if necessary by admixture with camauba or candelilla wax. In the examples which accompany this specicatiOn, Asiastic paraflin has been employed as typical of a highly satisfactory moistureproong gent, but it -is to be understood '(0 that -other moistureproong agents may be substituted. f

In the preparation 'of moistureprooiing coating compositions comprising a. cellulose nitrate and a moistureproong agent, it is advantageous to include some material which will improve the iin, petrolatum, ceresin, Japan wax, palm wax,

When the heat seal test described above is applied to sheets of regenerated cellulose coated with a moisture-proong coating composition such as that of'Example IV so that the total coating thickness is approximately r0.0001" (approximately 3 grams of composition solids per square meter for both sides), a heat sealing value of the order of 180 is obtained. 'Other examples which are typical of good heat scalable compositions may be chosen within the range 65 represented as satisfactory by means of the accompanying curves III and IV of Fig. 3 and comparable heat sealing values will be obtained. These heat sealing values are to be considered as merely illustrative of the bond strength attainable since it is obvious that greater or lesser bond strengths may have many useful applications, depending on the use to which the coated base material is put.

It is most convenient to apply the above moistureproong coating compositions to base materials such as sheets of regenerated cellulose by means of suitable solvents. Thus, the film-forming ingredients, conveniently considered as solids, indicated in any of the above examples may be dissolved to give a coating solution of appropriate viscosity and solids content whereupon the solution may be applied to the desired base in accordance with the methods known to the art. The solvents' may be removed and the coated base subjected to an elevated temperature at least equal to the melting point of the wax, whence, after cooling, a clear, transparent, moistureproof coated base will be obtained. A suitable technique for this operation is set forth in Charch and Prindle U. S. Patent No. 1,737,187 and since it is not a part of this invention, no further discussion seems necessary.

For the specific examples set forth, the following solvent mixtures may be successfully employed: A Table II Examples using pyroxyliu containing Solvent 11.5% N 12.5% N

' Range Preferred Range Preferred Percent Percent Percent Percent Ethyl alcohol 4-18 8 0-10 2 Toluene 24-50 33 25-50 37 Ethyl acetate -70 59 45-70 63 These solvent mixtures may be modied by the addition of other well known lacquer solvents to obtain special drying effects without in any way affecting the unique properties of dcyclohexyl phthalate or cyclohexyl acid phthalate as set forth in this specification.

These moistureproong compositions maybe applied to various sheet materials to produce wrapping tissues which are exible, moistureproof and heat sealable and which exhibit highly improved surface characteristics including excellent surface slip and resistance to caking, sticking or marring during storage. A variety of base sheet materials may be used such as cellulosic materials, paper, albuminous materials (gelatin, agaragar, casein), or lms made from rubber derivatives, e. g., lthe material prepared by reacting rubber and a metal halide` such as .boron triiluoride, stannous or stannic chloride, stannic acid, and other materials whichl are disclosed in an article by Thies and Clifford in the Journal of Industrial and Engineering Chemistry, vol. 26, page 123 (1934), the method of reacting the materials conforming to that disclosed in the said article referred to. In the preferred embodiment of the invention, a non-porous, nonfibrous, dense, smooth surfaced and preferably transparent material, such as regenerated cellulose, cellulose ester films including cellulose nitrate and cellulose acetate, or cellulose ether films including ethyl cellulose, benzyl cellulose, glycol cellulose or lowly etheried celluose, such as those `inv which there is only one substituent group for several glucose units of cellulose, is employed. It is obvious that suitable solvent adjustment will be made in the formulation of moistureproong coating compositions of the type described in order that there may be vno harmful effect on the base material employed.

Inv the coating compositions set forth in the above examples it is apparent that the proporaovasvs tions ofthe several ingredients may be varied over a considerable range. Thus, the cellulose nitrate may comprise 40-65% or more of the total solids although in most instances l5-55% will be found most satisfactory with approximately a convenient, generally useful proportion. The ratio of cellulose nitrate to blending agent may vary over a wide range from 2: 1 to 8:1, or even greater, b ut, for most purposes,l a ratio from 3:1 to 7:1 is satisfactory while a. ratio of 4:1 is convenient and yields generally goodresults. The cellulose nitrate is usually in excess of the total plasticizer content and the ratio of cellulose nitrate to plasticizer may vary from 1:1 to 3:1, but a ratio of 1.5:1 to 2:1 is generally found to give the best results.

The blending agentV may vary according to the cellulose nitrate, plasticizer or `moistureprooflng agent employed and it may constitute 120% or more of the total solids. When highly heat sealable compositions are desired, the amount of blending agent is preferably low and may comprise 5-10% or less of the total solids. The ratio of blending agent to moistureproolng agent may vary from 1:5 or less to 5:1 or more, and usually a ratio of approximately 3:1 to 4:1 will be found satisfactory. The larger amounts of blending agent are usually used when the blending agent exerts some plasticizing action .and can therefore replace a portion of the plasticizer.

The moistureproong agent is usually present in a quantity suflicient to impart a suitable degree of moistureproofness while still maintaining homogeneity of composition so that the ultimate moistureproong coating on the moistureproof article prepared in accordance with the invention will be clear, transparent, non-greasy, nonsmeary and non-tacky under the normal conditions of handling or storage. Generally speaking, if the moistureproong agent constitutes less than 10% of the total solids, these conditions will be fullled but while 2-6% of moistureproofing agent has been found to yield excellent results, it is to be understood that more or less may be used, depending on the nature of the moistureproong agent.

The plasticizer must be either dcyclohexyl phthalate or cyclohexyl acid phthalate or a mixture of plasticizers containing appreciable quantities of one or both of these specific compounds if the objects of the invention are to be accomplished. The total plasticizer concentration may vary from 2.045% of the total solids. Low percentages of plasticizer, however, are usually used only when the blending agent is capable of exert-- ing a plasticizing action and can therefore substitute for a portion of plasticizer which might otherwise be added. Among the objects of this invention is the production of highly moistureproof and preferably highly heat sealable coating compositions and for the accomplishment of Usually, 50%l or more of these specific piasticizers. Because of the desired high percentage of plasticizer in the total composition the ratio of plasticizer to moistureproofing agent may be quite high, in some instances amounting to as much as 20:1. On the other hand, if a plasticizing-blending agent is used, the ratio of plasticizer to moistureprooiing agent may fall as low as 6:1. Usually, a ratio of 7 :1 to 10:1 will be found to serve satisfactorily.

In the preceding discussion of the proportions of ingredients in the coating compositions the ranges of percentage composition or ratio have been given to facilitate the formulation of highly satisfactory and preferred compositions, and to aid one skilled in the art in quickly and Ieasily arriving at operable compositions not specifically described in the examples. It is to be understood, however, that these limiting ranges are largely illustrative and do not restrict the invention beyond the limitations set forth in the appended claims.

Numerous advantages of the invention may be observed by reference to the accompanying drawings.

Referring to Fig. 1, a series of curves will be observed which represent the change in permeability value for a given moistureproong composition with increasing plasticizer concentration. 'I'he curves were all obtained by substituting different plasticizers in the same basic composition in which latter the moistureproong agent constituted 4% of the total solids while the ratio of cellulose nitrate to blending agent remained constant at 4:1. Nitrocellulose containing 11.5%

'nitrogen was used. Curve'I represents the re- ,tendency to cake, stick or smear during storage.

It is apparent that increase in plasticizer content increases moistureproofness, as is evidenced by the marked decrease in permeability value. It will be noted however that in the range of high moistureproofness (permeability values of 40 or less), both Curves I and II show that increase of piasticizer concentration is detrimental to the surface characteristics of the coating compositions. Thus, the use of more than 29% dibutyl phthalate or 32% of tricresyl phosphateresults in the production of a soft and sticky coating composition. On the other hand, curve III shows that the specific plasticizers of this invention continue to improve the moistureproofness without any harmful effects on the surface characterlstics. `Fig.`2 illustrates the same points as Fig. 1, using a nitrocellulose-having a nitrogen content of 12.5%. Here again, the curve III denitely indicates the superiority of dicyclohexyl phthalate or cyclohexyl acid phthalate as plasticizers -foi highly moistureproof coating compositions having extraordinary surface characteristics.

Fig provides a series of curves obtained from a study of coating compositions formulated to secure good heat sealing properties in addition to moistureproofne'ss and good surface characteristics. All of thesecompositions contained 3% Asiatic paraiiin as the moistureproong agent, 7% damar (dewaxed) as the blending agent and suiiicient pyroxylin f 11.5% nitrogen content. The broken portions of the curves represent compositions having unsatisfactory heat sealing power as defined above. It is apparent that satisfactory heat sealing cannot be obtained with dibutyl phthalate or tricresyl phosphate (curves I and II) until the plasticizer content is in excess of approximately 35%. Dicyclohexyl phthalate alone (curve IV) is satisfactory over 38% and the mixed plasticizer of curve III-becomes eiective at about the same concentration.

The curves represented in Fig. 4 are identical with those of Fig. 3 but the broken portions indicate compositions which show unsatisfactory surface characteristics.

A comparison of the curves in Figs. 3 and 4 reveals that in the curves I and II compositions having satisfactory heat sealing properties have unsatisfactory surface characteristics. As a matter of fact, in both.curves the critical point for good surface is passed before a satisfactory heat seal is reached. On the other hand, compositions plasticized wholly or in partby dicyclohexyl ,phthalate (curves III and IV) show good surface characteristics throughout the entire range.

From the foregoing, it is apparent that moistureproofing coating compositions comprising a cellulose nitrate, a moistureprooiing agent and a blending agent, and plasticized wholly or in part by means of dicyclohexyl phthalate or cyclohexyl acid phthalate possess numerous advantages over the prior art, making possible the production of moistureproof sheet materials suitable for use as wrapping tissues which have superior qualities. Sheet materials coated with these compositions have excellent surface slip and are highly resistant to caking, sticking or smearing under conditions normal to storage. When the base sheet material is transparent, the final product is also transparent unless the coating compositions are deliberately modified to produce opaque, colored or otherwise preferred effects. The compositions, and hence the coated sheet materials. can be made moistureproof over a comparatively wide range of permeability values and where a high degree of moistureproofness is desired, this too can be obtained without deleteriously affecting the surface characteristics of the product. At the same time a highly heat sealable wrapping tissue with high moistureproofness and good surface characteristics may be obtained. The unique effect of these specific plasticizing agents is highly unobvious and their use provides new and useful moistureproong coating compositions and coated sheet materials, thus constituting a marked advance in the art. Y

Where percentages and proportions are referred to throughout the specidcation, they represent parts by weight unless indicated otherwise.

Any modification or variation of the invention as described above, which conforms to the spirit of the invention, is intended to be included within the scope of the claims.

1. A heat scalable, moistureproof, non-porous, non-fibrous, wrapping tissue having good surface slip and good storage characteristics, comprising a non-porous, non-brous base and a coating thereon containing pyroxylin containing 10.5 to 11.5% nitrogen, a wax material, a blending agent and a plasticizer comprising dicyclohexyl phthalate, the Dyroxylin comprising about 4065% of the total solids in the coating, the pyroxylinblending'ag'ent ratio beingfrom 2:1 to 8:1, the

pyroxylin-plasticizer ratio being about 1:1 to 3:1, and the blending agent wax material ratio being about 1:5 to 5:1.

2. A heat sealable, moistureproof, non-porous, non-brous, wrapping tissue having good surface slip and good storage characteristics, comprising a non-porous, non-brous base and a coating thereon containing pyroxylin containing 10.5 to 1 1.5%'nitrogen, a wax material, a blending agent and a plasticizer comprising dicyclohexyl phthalate, the pyroxylin comprising about 45-55% of the total solids in the coating, the pyroxylin-blending agent ratio being about 41:1, the pyroxylin-plasticizer ratio being about 1.5:1 to 2:1, the blending agent wax material ratio being about 3:1 to 4:1, being further characterized in that the plasticizer is predominantly a cyclohexyl phthalate.

3. A moistureproong coating composition which is heat-sealable when dry comprising pyroxylin containing 10.5 to 11.5% nitrogen, a Wax material, a resin and a plasticizer comprising dicyclohexyl phthalate, the pyroxylin comprising about I0-65% of the total solids, the pyroxylinblending'agent ratio being from,2:l to 8:1, the pyroxylin-plasticizer ratio being about 1:1 to 3:1, and the blending agent wax material ratio being about 1:5 to 5:1. l

4. A moistureproong coating composition which is heat-sealable when dry comprising pyroxylin containing 10.5 to 11.5% nitrogen, a Wax material, a resin and a plasticizer comprising dicyclohexyl phthalate, the pyroxylin comprising about 45-55% of the total solids, the pyroxylinblending agent ratio being about 4:1, the pyroxylin-plasticizer ratio lbeing about 1.5:1 to 2:1 'the blending agent wax material ratio being about 3:1 to 4:1, being further characterized in that the plasticizer is predominantly a cyclohexyl phthalate.

5. A transparent heat sealable, moistureproof, non-ibrous, substantially non-porous pellicle, having good surface slip and good storage characteristics, comprising a non-porous, non-fibrous base and` a moistureproong 'coating thereon containing a Wax material, pyroxylin, and a plasticizer taken from the group consisting of dicyclohexyl phthalate and cyclohexyl phthalate, the pyroxylin comprising 40 to 65% of the total solids of the coating, and the pyroxylinplasticizer ratio ranging from about 1:1 to 3:1.

6. A transparent, heat sealable, moistureproof, non-fibrous, substantially non-porous pellicle having good surface`slip and good storage characteristics, comprising a regenerated cellulose base and a moistureproong coating thereon containing a wax material, pyroxylin, and a plasticizer composed of a mixture of a liquid plasticizer and a solid plasticizer, the solid plasticizer takenv from the group consisting of dicyclohexyl phthalate and cyclohexyl acid phthalate, in which the solid plasticizer predominates, the pyroxylin comprising 40 to 65% of the total solids of the coating, and the pyroxylinplasticizer ratio ranging from about 1:1 to 3:1.

7. A` moistureproong coating composition which is heat sealable when dry comprising pyroxylin, a wax material, and a plasticizer taken from the group consisting of'dicyclohexyl phthalate and cyclohexyl acid phthalate, the pyroxylin comprising 40 to 65% of the total solids of the coating, and the pyroxylin-plasticizer ratio ranging from about 1:1 to 3:1.

8. A moistureproong coating composition which is heat sealable when dry comprising pyroxylin, a Wax material, and a plasticizer composed of a mixture of a liquid plasticizer and a solid plasticizer, the solid plastic1zer taken from the group consisting' of dicyclohexyl phthalate and cyclohexyl acid phthalate, in which the solid plasticizer predominates, the pyroxylin comprising 40 to 65% .of the total solids of' the coating, and the pyroxylin-plasticizer ratio ranging from about 1:1 to 3:1.

JAMES A.4 MITCHELL. 

